Preheat oven to 375 degrees Fahrenheit. This cake batter makes 12 large 4-inch cupcakes or 24 standard sized cupcakes. Only butter the bottoms of the muffin tins. Don’t put butter on the sides-that will stop the batter from climbing up. Angel food cake cools suspended upside down, so it’s best not to use cupcake liners because they will fall right out of the tins.
Whisk a 1/2 cup + 2 tablespoons sugar and 1 cup cake flour together in a medium bowl. Set aside.
Whisk the rest of the sugar (1/2 cup + 2 tablespoons) and the salt in a small bowl. Set aside.
In a large stainless steal or glass bowl use a beater with a whisk attachment to whip the egg whites and cream of tartar together on medium-low speed until foamy, about 1 minute.
Increase the speed to medium-high and whip the egg whites until they are soft and billowy mounds, about 1 minute.
Gradually whip in the sugar and salt mixture a tablespoon at a time, about 1 minute.
Keep whipping the whites until they are shiny and have formed soft peaks, 1 to 3 minutes.
Fold in the water, lemon juice, and vanilla extract by hand.
Sift 1/4 cup of the flour mixture over the top of the whites and gently fold together with a large rubber spatula until there are just a few streaks of flour remaining. Repeat with the remaining flour mixture a 1/4 cup at a time.
Fill the cupcake tins 3/4 of the way full, trying your best to pour equally.
Bake the large cupcakes for 30 minutes and the small cupcakes for 20 to 25 minutes.
Turn the muffin tins upside down and suspend them. I placed the edges of the muffin tins onto mason jars. Let the cupcakes cool hanging upside down for 2 hours. You will have to run a knife along the edges to get the cupcakes out.